void TransformFrustum(Plane Frustum[6], const matrix& obj_to_view)
// Given a transformation matrix from object space to view space,
// this function transforms the given view-space frustum into object-space,
// so that clipping/culling can be done in object space.
{
int i;
vec3 n, p, q;
for (i = 0; i < 6; i++) {
// There's a faster, more direct way to do this. Deal with later.
obj_to_view.ApplyInverseRotation(&n, Frustum[i].Normal);
p = Frustum[i].Normal * Frustum[i].D;
obj_to_view.ApplyInverse(&q, p);
Frustum[i].Normal = n;
Frustum[i].D = n * q;
}
}
